Chemokine C-C motif ligand 33 is a key regulator of teleost fish barbel development

Barbels are important sensory organs for food seeking of teleosts, reptiles, and amphibians, but the molecular basis of barbel development is unknown. Here, we exploited the barbel-less bottlenose catfish as a natural model to determine the genomic basis for barbel development. Through a series of comparative analyses using genome and transcriptome datasets, a chemokine gene, ccl33, was identified as a key regulator of barbel development. Its knockout in zebrafish led to the loss of barbels, further supporting the roles of ccl33 for barbel development. These findings demand functional studies of chemokines as key developmental, as well as immune, regulators.